Method, device and system for transmitting data

A method, a device and a system for transmitting data are provided by the embodiments of the present invention. Said method includes: the first network element obtains the relationship between the identifier of a user equipment (UE) and the username of the UE; according to the first connection corresponding to the identifier of the UE and the second connection corresponding to the username of the UE, said first network element transmits the data of the UE.